Is it reasonable to do a combination of closed-cell spray foam in the unfinished attic rafters and batts on the ceiling flats?
Reasoning for this is to (a) get HVAC in the attic within the envelope where rafters can’t be properly vented, and (b) still have insulation on top of the flat ceiling drywall because there is some ceiling-radiant heat. And there’s the added benefit of getting some of the R value from a cheaper product.
Does the R38 code requirement allow the insulation to be in two different places as long as it totals the appropriate R-value?
Also, should the minimum depth of spray foam be 3 inches to control condensation against the roof sheathing? (Am in climate zone 5)
GBA Detail Library
A collection of one thousand construction details organized by climate and house part